Question

How would a second amino acid bond to cysteine?

Answer 1

Amino acids are small molecules that are the building blocks of proteins.

• Protein serves as structural support inside the cell and they perform many vital ( very important or necessary) chemical reactions.
• Each protein is a molecule made up of different combinations of 20 types of smaller, simpler amino acids.
• Amino acids are made up of a basic amino group ($-{\mathrm{NH}}_2$), an acidic carboxyl group ($-\mathrm{COOH}$), and an organic R group ( or side chain) and it is unique to each amino acid.
• Our body needs 20 different amino acids to function correctly.
• These 20 amino acids combine in different ways to make proteins in our body.
• Amino acids can be placed under three different groups.

1. Nonessential amino acids: These are produced naturally by our body and have nothing to do with the food we eat. Examples of nonessential amino acids: are alanine, asparagine, aspartic acid, and glutamic acid.
2. Essential amino acids: These can't be produced by the body and must come from the food you eat. If we don't eat food that contains essential amino acids, our body won't have them. Examples of essential amino acids: are lysine, leucine, histidine, methionine, phenylalanine, threonine, tryptophan, valine and isoleucine.
3. Conditional amino acids: These are usually not essential to everyday living but are important when you are sick, injured, or stressed. Examples of conditional amino acids: are cysteine, arginine, glutamine, tyrosine, glycine, ornithine, proline and serine.

• Cysteine is the only amino acid that is only capable to form a covalent bond with the help of its side chain.
• If two cysteine side chains end up next to each other because of folding in the peptide chain, they can react to form a sulphur bridge.